This invention relates to aggregate products and more particularly to the application of particulate or aggregate to surfaces such as road or wall surfaces.
In road building and maintenance, reflective stripes and roadmarkings must be applied in accordance with strict specifications as to hardness, abrasiveness, wear resistance, cure-time of resin used and the like. For example, the placing of reflectorized traffic stripes and markings requires specific thermoplastic compounds with pigments, glass spheres, and filler being well dispersed in the resin. Further requirements as to color retention, water absorption, etc., must be met. At present, traffic striping and road marking is accomplished by using a hot-melt process in which the road pavement is pre-heated prior to application of resinous material containing the pigment, filler, and other required additives. Special kettles and applicators must be provided for melting, heating, and applying the molten thermoplastic material. Hand applicator equipment must be insulated and have sufficient capacity and yet be sufficiently maneuverable to install cross walks, lane, edge, and center lines, as well as arrows and legends. Application time, weather limitations and surface preparation, as well as the use of sealing primer, must also be considered in order to insure an acceptable finished product.
While the hot-melt process has proven to be valuable in that the resinous composition cures almost instantly upon cooling, it has also been shown to be less than satisfactory for a number of reasons. An especially significant disadvantage has been the slipperiness of the finished product under any damp conditions. The addition of glass beads to the resinous material after its application to the road surface and prior to its curing, as in accordance with specifications, is not designed to remedy such situation, and there are at present no abrasive or non-skid additives which eliminate skidding in the finished product.
Moreover, the cost of the hot-melt process is extremely high. Raw material must be purchased in precast block form. Packaging in cartons is required to avoid sticking together of the raw material. In addition to the cost of raw material, considerable additional expenditures are required for applicator equipment as well as for equipment to pre-heat by open flame the road pavement ahead of the applicator equipment. And in addition to the slipperiness, the finished product has been found to fail in adhesiveness, to become embrittled under icy conditions, and to break up under the impact of snow plows.
In addition to the area of traffic striping and road marking, the application of aggregate or particulate to structural walls, floors, or the like, whether for decorative effect or for wearing purposes, has proven to be difficult or costly, or both. Too often, the methods of application of aggregate to such surfaces requires time-consuming operations, such as with a terrazzo tile application, with the result that labor costs are prohibitive. That is, there has not been available any low-cost and readily usable method for applying any of a wide range of aggregates to surfaces.